In between a velocity selector (3)
is placed. The dimensions of the velocity selector are identical
to those of the selector developed by Trujillo et al.
The theory for this type of selector can easily be extended to
beams with an angular spread due to the finite width of the
collimating slits . This leads to a value of the velocity spread.
Alignment and calibration
The selector was carefully aligned by a
cathetometer and this alignment was checked by measuring the
velocity distribution of a potassium beam produced by a thermal
oven, the temperature of which was measured by platinum
The accuracy of the nominal energy is determined by the
alignment and calibration of the velocity selector. This is
estimated to be 1%, much less than the energy spread.